Many controversial issues lend themselves to split-the-difference compromises, but the Keystone XL pipeline isn't one of them. That puts President Obama in a tough spot as his administration nears a decision on the proposed $7 billion project, which would carry tar-sand oil from Canada to Gulf Coast refineries.

For the environmentalists who strongly supported Obama's re-election, Keystone has become a crucial test of his promises to take climate change seriously. Thousands demonstrated in Washington on Sunday against the project, asserting that the pipeline would unlock so much dirty oil that it would be "game over" for the globe if the project proceeds.

For Canada, whose government badly wants the pipeline to go forward, the decision is an equally crucial test of the two neighbors' relationship. And for the United States, the project offers a rare opportunity to create jobs and lessen the nation's decades-long dependence on oil from unstable or unfriendly suppliers.

Both sides make strong arguments, but after more than four years of exhaustive study, the right answer on Keystone remains: Build it.

At a time of rising global competition for energy resources, the pipeline would bring reliable new oil supplies to a U.S. that still imports 40% of its crude, 7.6 million barrels a day last year. And 40% of those imports come from OPEC nations such as Venezuela, Iraq and Nigeria. Keystone is expected to supply 830,000 million barrels a day, a key step toward the long-sought goal of North American energy independence, which suddenly seems attainable.

Much of the opposition to Keystone has come from critics who say running a big pipeline through the heart of the USA is too risky. Haven't they noticed that tens of thousands of miles of oil pipelines already crisscross the United States? As long as the nation's quarter-billion vehicles rely almost exclusively on gasoline and diesel, pipelines are the safest and most efficient way to move it.

Obama delayed a final decision on Keystone last year, in part to allow a rerouting around environmentally sensitive areas in Nebraska. That has been accomplished, and Nebraska's governor signed off on the new map last month.

Nor would blocking Keystone keep the tar-sands oil in the ground. In a world starving for oil, it's overwhelmingly likely the oil would find another way to market - through a pipeline to West Coast ports to carry it to China, to East Coast ports to carry it to other nations, or by barge, rail and existing pipelines into the USA.

The goal of locking down tar-sands oil and stopping other forms of fossil fuel production such as fracking - as many protesters demanded in Sunday's demonstration - would be more compelling if the U.S. were ready to shift to renewable fuels such as solar, wind and biomass to power vehicles, heat homes and run factories. Last year, though, renewables supplied just 9.4% of all U.S. energy needs, despite robust tax incentives for wind power and electric cars. Shutting down conventional sources of energy at this point is naive and economically destructive.

Demand might be further reduced by making vehicles and buildings more efficient. A carbon tax or a cap-and-trade system could do the same by making the price of conventional fuels better reflect their cost to the environment.

Until that day, though, the best choice for the economy and the planet is to ensure ample, secure supplies of energy. The Keystone pipeline is an essential part of that strategy.